Safety device for a sheet-feeding device



Aug. 30, 1966 A. SCHWEBEL SAFETY DEVICE FOR A SHEET-FEEDING DEVICE 2 Shee ts-Sheet 1 Filed July 16, L964 INVENTOR ADOL F SCHWEHEL ATTORNEY A. SCHWEBEL SAFETY DEVICE FOR A SHEET-FEEDING DEVICE Aug. 30, 1966 2 Sheets-Sheet 2 Filed July 16, L964 INVENTOR A0011 SCHWEHEL BY $0.9M.

ATTORNEY United States Patent 3,269,725 SAFETY DEVICE F011 A SHEET-FEEDING DEVICE Adolf Schwebel, Offenbach-am-Main, Germany, assignor to Maheg Maschinenbau G.m.b.H., Nachf. Hense. & Pleines G.m.b.H. & Co, Offenbach-am-Main, Germany, a company of Germany Filed July 16, 1964, Ser No. 383,141 Claims priority, application Germany, July 20, 1963, M 57,570 8 Claims. (Cl. 27162) The present invention relates to sheet-feeding devices and, more particularly, to sheet-feeding devices for continuous feeding of stacks or piles of sheets and with two stack lifting means, one of which lifts a newly fed full stack and the other lifts the depleted stack from which successive sheets are Withdrawn by a sheet pick-up device.

It is known to equip sheet-feeding devices of the general kind herein referred to with a safety device which is activated when a newly fed full stack is positioned under the more or less depleted stack and is lifted into its correct position. The safety device when activated stops further lifting of the full stack.

Safety devices as heretofore known comprise a springloaded switch controlling the power supply of the lifting means for the full stack and controlled by a springy safety bar which coacts with the full stack and, more specifically, with the top surface thereof to effect opening of the switch when the full stack reaches its correct position. A safety device of this kind pre-supposes that the top surface of the full stack is substantially flat. Practical experience shows that this is by no means always the case, but that part of the top surface of the full stack may protrude from the remainder of the surface due to bulging or other deformation of the top layers of sheets. Such protruding portions of the full stack may cause lifting of the depleted stack to an extent sufficient to dam-age the sheet pick-up device before the switch bar engaged with a fiat surface portion of the full stack will effect stopping of the lifting means for the full stack.

It is a broad object of the invention to provide a novel and improved safety device for sheet-feeding devices of the general kind above-referred to which will stop the lifting of the full stack not only when the same reaches its correct position in reference to the depleted stack, but also when a protruding surface portion of the full stack prematurely engages the depleted stack and lifts the same thereby eliminating the danger of damage to the sheet pick-up device.

A more specific object of the invention is to provide a novel and improved safety device for sheet-feeding devices Which does not require any direct contact with the full stack, but probes the lifting means for the depleted stack and operates the cut-off switch of the lifting means for the full stack when the condition of the lifting means for the depleted stack indicates lifting of said stack by the full stack.

Another more specific object of the invention is to provide a novel and improved safety device for a sheet-feeding device which is mounted on the stationary frame structure of the sheet feeding device, thereby obviating the need for easily damaged loose electrical connections to and from the cut-off switch for the lifting means for lifting the full stack.

Still another more specific object of the invention is to provide a novel and improved safety device for sheetfeeding devices which is capable of safely operating at high operational speeds and which is free of delicate components that are easily damaged and thus cause failure of the operation.

Other objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims constituting part of the application.

In the accompanying drawing several preferred embodiments of the invention are shown by way of illustration and not by way of limitation.

In the drawing:

FIG. 1 is an elevational diagrammatic view of a sheetfeeding device equipped with a safety device according to the invention.

FIG. 2 shows diagrammatically a modification of the safety device.

FIG. 3 is a circuit diagram for use with safety devices according to the invention.

FIG. 4 is a modification of the circuit diagram of FIG. 3.

FIG. 5 shows another modification of the safety device, and

FIG. 6 shows still another modification of the safety device.

Referring first to FIG. 1 in detail, the full stack 1 is supported on a table 2 which, in turn, is suspended on suitable bendable suspension means such as chains 3 which are guided on chain wheels 4 and 5. Chain wheel 4 should be visualized as being continuously or step by step driven by a motor (not shown) to effect a corresponding lifting of table 2 and with it of stack 1. The terminals of the motor are indicated at 24 and 25. Stack 1 rests with one of its side edges against guide rails or bars 6 to guide the stack while being lifted.

The second stack 10 from which sheets are being successively withdrawn during operation and which is hence more or less depleted rests on bars or rods 11. These bars in turn are supported and guided by a slide 8 slidable in a track 8a and if desired by a safety or control guide 7. Guide 7 and slide 8 are suspended from suitable bendable suspension means such as chains 13 which in turn are guided over chain gears 40 and 41, one of which should be visualized as being power driven. As it is evident, chains 13 will be tensioned when supporting the weight of depleted stack and will be slack when stack 10 is lifted without correspondingly pulling up chains 13. Successive sheets are withdrawn from the top surface of stack 10 by a suitable and conventional pick-up device 12 indicated as a suction cup.

All the hereinbefore described structural components of the sheet feeding device are conventional and should be visualized as being mounted on the frame of the sheetfeeding device which is not shown in detail to simplify the illustration.

Turning now to the safety device according to the invention, this device comprises a roller 14 which is urged by a spring 15 against the righthand chain 13 in a direction substantially transverse to the direction of movement of the chain. Spring 15 is accommodated in a housing 52. The spring abuts at one end against an end wall of the housing and at the other end against a shoulder on a rod 16 supporting roller 14 and lengthwise slidable in housing 52. Rod 16 has at its end opposite to the one supporting roller 14 a lengthwise threaded bore into which is screwed a set screw 17 to vary the effective length of the rod by the setting of screw 17 A locknut 18 may be provided to secure set screw 17 in its adjusted position. The head of set screw 17 coacts with a roller 20 supported on a bar 42 which constitutes part of a switch 19 and supports for this purpose a contact arm 21. This bridge is engageable with switch contacts 22 and 23 which are included in an energizing circuit connecting motor terminals 24 and 25 with a power line 43. A spring 44 urges switch bar 42 into a position in which contact arm 21 is disengaged from switch contacts 22 and 23 and roller 20 abuts against set screw 17. A second weaker spring 44a counteracting spring 44 may be provided. The safety device is also mounted on the frame structure of the device and in a position such that it is physically separated from the two stacks or piles 1 and 10. The hereinbefore described switch arrangement is such that pressure roller 14 will force switch bar 42 into its switch closing position when the respective chain 13 is tensioned, that is, when it is substantially straight due to the weight of stack suspended thereon. Whenthe chain becomes slack due to a lifting of stack 10 by stack 1, roller 14 Will follow the chain and thereby permit opening of the switch contacts by the action. of springs 15 and 44. FIG. 1 shows the chain 13 in its slack condition. Hence switch 19 is open and the power drive for lifting the full stack 1 is interrupted.

The operation of the safety device as hereinbefore described, is as follows:

Let it be assumed that the top surface of full stack 1 is not flat as it should be, but turned up at a corner 1a. As is evident, corner 1a will come in contact with bars 11 prior to the flat area of the top surface of stack 1 and thereby causing premature lifting of depleted stack 10. A safety device using a spring control bar as heretofore known would not respond to such premature lifting of stack 10 since it would, or at least may detect only the flat surface portion of stack 1 which is still out of contact with depleted stack 10. However, a safety device according to the invention will automatically and immediately res-pond due to the slackening of the respective chain 13 causing opening of switch contacts 22 and 23 as previously described as soon as depleted stack 10 is lifted by the turned up corner 1a, thereby preventing damage to pick-up means 12.

FIG. 2 shows a safety switch employing the same principle but somewhat different in details. The safety switch according to FIG. 2 comprises a bell crank lever 45 pivotal about a pivot pin 46. One arm 28 of the lever mounts a pressure roller 25 corresponding to previously described pressure roller 14 and the other arm 28a coacts by means of a set screw 27 with an arm 29 also pivotal about pivot pin 46. Arm 29 controls switch contacts 30 and 31 which, in turn, control the energizing circuit for motor terminals 24 and 25. The entire system is loaded by a spring 26. As it is evident, set screw 27 permits adjustment of the relative positions of lever arm 28a and switch arm 29 and with it the extent of slack of chain 13 at which the switch contacts will be opened or closed.

The function of the safety device according to FIG. 2 is evident from the previous description.

Safety devices as hereinbefore described may be provided for each of the chains 13 for the depleted stack 10. FIG. 3 shows two safety devices connected in parallel and FIG. 4 shows two safety devices serially connected. Connection of two safety devices in parallel, as is shown in FIG. 3, prevents lifting of stack 10 to a level at which it would damage pick-up device 12.

FIG. 5 shows a safety switch similar to that shown in FIG. 1. The general structure and function of the safety device of FIG. 5 are evident from the description of FIG. 1. The device of FIG. 5 is provided with means for rendering the response of the switch more sensitive, thereby permitting a more accurate adjustment of the safety device. For this purpose rod 16 is mounted and slidably guided in a housing 33 in which is threaded to receive an adjusting or tensioning nut 34. This nut, by its position relative to housing 33, controls the loading of spring 15 which, in turn, controls the coaction of pressure roller 14 with chain 13. Nut 34 can be conveniently adjusted by a suitable tool applied to the flat key surfaces 35 of the nut.

As it is evident, the loading of spring 15 may be adjusted by means of nut 34 in accordance with the weight of structural components such as the stack table 2 and bars 11, which affect the tension of chain 13.

The safety device according to FIG. 6 is similar to the device of FIG. 2 but is rendered more sensitive than the device of FIG. 2 by providing adjusting means simi- 4 lar to the one described in connection with FIG. 5. According to FIG. 6 spring 26 which leads the entire system and abuts against a third arm 28b of bell crank lever 45 may be adjusted by means of a set screw 36, the function of which is evident from the previous description.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention, it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended therefore, to cover all such changes and modifications in the appended claims.

What is claimed as new and desired to be secured by Letters Patent is:

I claim:

1. A safety device for a sheet-feeding device of the kind having a frame structure, a power-driven main lifting means for lifting a full stack of sheets and an auxiliary lifting means for lifting a depleted stack of sheets disposed above said full stack, said auxiliary means including a bendable portion tensioned by the weight of the depleted stack, said safety device comprising a switch for cutting off the power drive for the main lifting means, said switch including yieldable means urging the switch into its open position; and a probe mounted on said frame structure for probing said auxiliary lifting means, said probe including a movable switch control member urged by said yieldable means toward and into engagement with the bendable portion of the auxiliary lifting means, said control member being movable between a position closing said switch against the action of said yieldable means and a position freeing the yieldable means for opening the switch, said bendable portion in a tensioned condition retaining said control member in its switch-closing position and in a slack condition due to lifting of the depleted stack freeing said control member for movement into its switch-opening position.

2. A safety device according to claim 1 wherein said movable switch control member comprises two aligned lengthwise displaceable rods, the free end of one of said rods engaging said bendable portion and the free end of the other rod mounting a contact arm controlling the opening and closing of said switch, said yieldable means urging said rods into abutment with each other and jointly into abutment with said bendable portion.

3. A safety device according to claim 2 wherein said bendable portion comprises an element yielding in its slack condition to a pressure in a direction longitudinally of the direction of displacement of said rods, and wherein the combined effective length of said rods is adjustable to vary the distance of displacement of the rods at which said switch is opened.

4. A safety device according to claim 3 wherein one of said rods comprises a lengthwise adjustable set screw for varying the effective length of said rod by the position of said set screw.

5. A safety device according to claim 1 wherein said movable switch control member comprises a pivotally supported bell crank lever, one arm of said lever being engaged with said bendable portion and the second arm controlling the opening and closing of said switch in ac cordance with the pivotal position of the bell crank lever which, in turn, is controlled by the condition of tension of said bendable portion.

6. A safety device according to claim 5 wherein said bell crank lever is pivotal about a pivot axis and a third arm is also pivotal about said axis, said third arm coacting with said switch, and wherein spring means urge said third arm and the second arm of said bell crank lever angularly toward each other, and a set screw on 5 6 either one of said arms controls the minimum angle be- References Cited by the Examiner tween Sald arms- UNITED STATES PATENTS 7. A safety device according to claim 1 and comprising regulating means coacting with said yieldable means 1,701,861 2/1929 Niblack' for varying the tension thereof. 5 2,970,835 2/1961 Schwebel 271-62 8. A safety device according to claim 7 wherein said OTHER REFERENCES yieldable means comprise a loaded coil spring abutting at one end against said probe and at the other end against Wheeler: Card Prfisence Indlcator for Hopperan abutment member, said abutment member being dis- In IBM disclosure 4 (2) i July 1961 TK placeable in the direction of the spring to vary the ad- 10 7800-113- ]llStmeIlt thefeof- ROBERT B. REEVES, Primary Examiner. 

1. A SAFETY DEVICE FOR A SHEET-FEEDING DEVICE OF THE KIND HAVING A FRAME STRUCTURE, A POWER-DRIVEN MAIN LIFTING MEANS FOR LIFTING A FULL STACK OF SHEETS AND AN AUXILIARY LIFTING MEANS FOR LIFTING A DEPLETED STACK OF SHEETS DISPOSED ABOVE SAID FULL STACK, SAID AUXILIARY MEANS INCLUDING A BENDABLE PORTION TENSIONED BY THE WEIGHT OF THE DEPLETED STACK, SAID SAFETY DEVICE COMPRISING A SWITCH FOR CUTTING OFF THE POWER DRIVE FOR THE MAIN LIFTING MEANS, SAID SWITCH INCLUDING YIELDABLE MEANS URGING THE SWITCH INTO ITS OPEN POSITION; AND A PROBE MOUNTED ON SAID FRAME STRUCTURE FOR PROBING SAID AUXILIARY LIFTING MEANS, SAID PROBE INCLUDING A MOVABLE SWITCH CONTROL MEMBER URGED BY SAID YIELDABLE MEANS TOWARD AND INTO ENGAGEMENT WITH THE BENDABLE PORTION OF THE AUXILIARY LIFTING MEANS, SAID CONTROL MEMBER BEING MOVABLE BETWEEN A POSITION CLOSING SAID SWITCH AGAINST THE ACTION OF SAID YIELDABLE MEANS AND A POSITION FREEING THE YIELDABLE MEANS FOR OPENING THE SWITCH, SAID BENDABLE PORTION IN A TENSIONED CONDITION RETAINING SAID CONTROL MEMBER IN ITS SWITCH-CLOSING POSITION AND IN A SLACK CONDITION DUE TO LIFTING OF THE DEPLETED STACK FREEING SAID CONTROL MEMBER FOR MOVEMENT INTO ITS SWITCH-OPENING POSITION. 